Abstract:

There is provided an induction cooker capable of detecting failures in an
infrared ray sensor with excellent accuracy. The induction cooker
includes an infrared-ray detection unit (6) which includes an
infrared-ray incidence section (6a) to detect an infrared ray entering
the infrared-ray incidence section, the infrared ray being radiated from
a bottom surface of a pan, passing through a top plate, and entering the
infrared-ray incidence section; a infrared-ray temperature calculation
unit (7) operable to calculate a temperature of the bottom surface of the
pan based on an output of the infrared-ray detection unit; a light
emitting unit (8) which is provided below the top plate and emits light
with a first luminance for indicating a position of the infrared-ray
incidence section (6a); and a failure detection unit (9) operable to
detect failures in the infrared-ray detection unit based on an amount of
a change of an output of the infrared-ray temperature calculation unit
which is based on an output of the light emitting unit. The failure
detection unit (9) controls the light emitting unit to emit light with a
second luminance higher than the first luminance and detects failures in
the infrared-ray detection unit based on whether or not an amount of an
increase in the output of the temperature calculation unit falls within a
predetermined range.

Claims:

1. An induction cooker comprising:a top plate made of a material capable
of transmitting an infrared ray;a heating coil operable to heat a pan
placed on the top plate;a control unit operable to control electric power
supplied to the heating coil;an infrared-ray detection unit that includes
an infrared-ray incidence section under the top plate to detect an
infrared ray entering the infrared-ray incidence section, the infrared
ray being radiated from a bottom surface of the pan, passing through the
top plate, and entering the infrared-ray incidence section;a temperature
calculation unit operable to calculate a temperature of the bottom
surface of the pan based on an output of the infrared-ray detection
unit;a light emitting unit operable to emit light with a first luminance
near the infrared-ray incidence section when viewed from above the top
plate, by irradiating a back surface of the top plate from below the top
plate with light, to indicate a position of the infrared-ray incidence
section; anda failure detection unit operable to detect a failure in the
infrared-ray detection unit based on an amount of a change of an output
of the temperature calculation unit which is based on an output of the
light emitting unit;wherein the light emitting unit includes a luminance
changing section operable to change the luminance of the light emission,
andthe failure detection unit controls the light emitting unit to emit
light with a second luminance higher than the first luminance and detects
a failure in the infrared-ray detection unit based on whether or not an
amount of an increase in the output of the temperature calculation unit
falls within a predetermined range.

2. The induction cooker according to claim 1, wherein the failure
detection unit performs failure detection by controlling the light
emitting unit to turn off the light.

3. The induction cooker according to claim 1, whereinthe failure detection
unit performs failure detection a plurality of times by controlling the
light emitting unit to blink on and off.

4. The induction cooker according to claim 1, whereinthe failure detection
unit acquires a plurality of output values from the infrared-ray
detection unit which are based on a predetermined amount of light
emission from the light emitting unit and performs failure detection only
when the output values from the infrared-ray detection unit fall within a
predetermined range.

5. The induction cooker according to claim 1, further comprising a shield
section operable to interrupt the infrared ray entering the infrared-ray
incidence section from the top plate while the failure detection unit
performs failure detection.

6. The induction cooker according to claim 1, wherein the failure
detection unit performs failure detection immediately before the control
unit starts heating.

7. The induction cooker according to claim 1, wherein the control unit
stops heating when the failure detection unit determines that there is a
failure in the infrared-ray detection unit.

8. The induction cooker according to claim 1, further comprising a
notification section operable to give notice that there is a failure in
the infrared-ray detection unit when the failure detection unit
determines that there is a failure in the infrared-ray detection unit.

Description:

TECHNICAL FIELD

[0001]The present invention relates to an induction cooker using an
infrared ray sensor for use in ordinary households or restaurants.

BACKGROUND ART

[0002]Conventional induction cookers have generally utilized methods for
indirectly detecting a temperature of a bottom of a pan, by bringing a
thermosensor such as a thermistor into contact with a top plate on which
the pan is placed. Further, as a detection method with more excellent
responsivity, there has been utilized a method for detecting intensity of
infrared rays outputted from a bottom of a pan, using an infrared ray
sensor. When an infrared ray sensor is used, there are cases where the
temperature cannot be accurately detected, as follows.

[0003]For example, when the infrared ray sensor is contaminated, it is
impossible to accurately detect the temperature. Therefore, there has
been contrived a method for determining the contamination of an infrared
ray sensor, using a contamination detection section formed from a
combination of an infrared-ray TED and a photo transistor, based on a
reduction of an amount of light reflected by the surface layer of the top
plate due to absorption of infrared rays by the contamination of the
infrared ray sensor. Further, there has been a method for detecting the
contamination of an infrared-ray receiving portion and correcting an
actual temperature of radiation from an object to be heated, by using a
temperature detected by the infrared ray sensor and a temperature
detected by a thermosensor which is thermally contacted with the object
to be heated (refer to Patent document 1, for example).

[0004]For example, when there is a failure in the infrared ray sensor, it
is impossible to accurately detect the temperature.

[0005]Therefore, there has been a method which determines that there is an
abnormality and stops heating or reducing the heating power, if a value
of an output of an infrared ray sensor exceeds a predetermined range.
Further, there has been contrived a method which provides a thermosensor
such as a thermistor for detecting the temperature of an infrared-ray
sensor or a peripheral temperature around the infrared ray sensor and
determines that there is an abnormality if the temperature from the
thermosensor exceeds a predetermined range (refer to Patent document 2,
for example).

[0006]Patent document 1: JP-A-2004-241218

[0007]Patent document 2: JP-A-2005-216585

DISCLOSURE OF INVENTION

Problems to be Solved by the Invention

[0008]However, in the related art, there has been a problem that an amount
of light entering the infrared ray sensor is changed depending on the
brightness of the top plate, presence or absence of a pan on the top
plate, and the temperature of the pan bottom, which makes it impossible
to successfully detect failures. Further, in the case of the structure
including an infrared ray LED and a photo transistor in addition to the
infrared ray sensor, the structure has been expensive and also has
required a large area for mounting the components and restricted the
shape of the heating coil, thereby reducing heating performance.

[0009]In the case of correcting the infrared ray sensor using the
thermosensor, when the temperature of the pan bottom is lower, there are
small differences among amounts of infrared rays which can be detected
along with the temperature, which has induced a problem that an object to
be heated has to be actually heated to a high temperature, otherwise it
is impossible to perform correction using the thermosensor and detection
of the contamination of the light receiving portion of the infrared ray
sensor. Further, there has been a problem that, in cases where the pan
bottom has been largely deformed or the like, it is hard to accurately
detect the temperature of the pan bottom, even if correction is performed
with the thermosensor. Further, there has been a problem that it is
significantly hard to limit the range of the output of the infrared ray
sensor, due to an influence of disturbing light.

[0010]As described above, with conventional methods, it has been
impossible to detect failures in an infrared ray sensor with excellent
accuracy.

[0011]The present invention has been made in to solve the aforementioned
problems in the related art and aims at providing an induction cooker
capable of detecting failures in an infrared ray sensor with excellent
accuracy.

Means for Solving the Problems

[0012]In order to solve the conventional problems, an induction cooker
according to the present invention includes: a top plate made of a
material capable of transmitting an infrared ray; a heating coil operable
to heat a pan placed on the top plate; a control unit operable to control
electric power supplied to the heating coil; an infrared-ray detection
unit which includes an infrared-ray incidence section below the top plate
to detect an infrared ray entering the infrared-ray incidence section,
the infrared ray being radiated from a bottom surface of the pan, passing
through the top plate, and entering the infrared-ray incidence section; a
temperature calculation unit operable to calculate a temperature of the
bottom surface of the pan based on an output of the infrared-ray
detection unit; a light emitting unit operable to emit light with a first
luminance near the infrared-ray incidence section when viewed from above
the top plate by irradiating the back surface of the top plate from below
the top plate with light, to indicate a position of the infrared-ray
incidence section; and a failure detection unit operable to detect a
failure in the infrared-ray detection unit based on an amount of a change
of an output of the temperature calculation unit which is based on an
output of the light emitting unit. The light emitting unit includes a
luminance changing section operable to change the luminance of the light
emission, and the failure detection unit controls the light emitting unit
to emit light with a second luminance higher than the first luminance and
detects a failure in the infrared-ray detection unit, based on whether or
not an amount of an increase in the output of the temperature calculation
unit falls within a predetermined range.

[0013]The failure detection unit performs failure detection by controlling
the light emitting unit to emit light with a high luminance through the
luminance changing section. This can increase detection accuracy of the
failure detection.

[0014]Further, it is possible to employ a structure which the infrared-ray
incidence section is covered with a pan when the light emitting unit is
covered with the pan, for example, a structure which provides the
infrared-ray incidence section between the center of the heating coil and
the light emitting unit on a straight line connecting the center of the
heating coil with the light emitting unit. In this case, when the pan is
not positioned over the infrared-ray incidence section, a user can easily
recognize that the pan is not positioned over the infrared-ray incidence
section through the light emission from the light emitting unit. That is,
the light emission from the light emitting unit functions to urge the
user to place the pan over the infrared-ray incidence section.
Accordingly, since the failure detection is performed with the
high-luminance light emission before start of heating, it is possible to
offer the effect of causing the pan to be placed at an appropriate
position, thereby further improving the accuracy of detection of infrared
rays by the infrared-ray detection unit, after the start of heating.

[0015]The failure detection unit may perform failure detection by
controlling the light emitting unit to turn off the light.

[0016]The failure detection unit may perform failure detection a plurality
of times by controlling the light emitting unit to blink on and off. This
can increase the accuracy of failure detection and also improve a visual
effect.

[0017]The failure detection unit may acquire a plurality of output values
from the infrared-ray detection unit which are based on a predetermined
amount of light emission from the light emitting unit and perform failure
detection only when the output values from the infrared-ray detection
unit fall within a predetermined range. This can reduce the occurrence of
erroneous detections. For example, it is possible to prevent erroneous
failure detections at a state where a person moves and disturbing light
is changed.

[0018]The induction cooker may further include a shield section operable
to interrupt the infrared ray entering the infrared-ray incidence section
from the top plate, while the failure detection unit performs failure
detection.

[0019]The failure detection unit performs failure detection, immediately
before the control unit starts heating. This enables detection of
failures immediately before the use of the cooker at all times, thereby
improving the safety.

[0020]When the failure detection unit determines that there is a failure
in the infrared-ray detection unit, the control unit may stop heating.
This can improve the safety.

[0021]The induction cooker may further include a notification section
operable to give notice that there is a failure in the infrared-ray
detection unit when the failure detection unit determines that there is a
failure in the infrared-ray detection unit. For example, it is possible
to inform the user of the fact that there is a failure in the
infrared-ray detection unit, through an LCD, a buzzer or a voice
notification. This can improve the safety.

EFFECTS OF THE INVENTION

[0022]According to the induction cooker of the present invention, the
detection of failures in the infrared-ray detection unit is performed
based on the amount of the change of the output of the temperature
calculation unit which is based on the output of the light emitting unit.
This enables detection of failures in the infrared-ray detection unit
with excellent accuracy.

BRIEF DESCRIPTION OF DRAWINGS

[0023]FIG. 1 is a block diagram of an induction cooker according to an
embodiment of the present invention.

[0024]FIG. 2 is a top view of a top plate according to the embodiment of
the present invention.

[0043]Hereinafter, an embodiment of the present invention will be
described, with reference to the drawings. Note that the present
invention is not intended to be limited to the embodiment.

1. Structure of Induction Cooker

[0044]FIG. 1 is a block diagram illustrating a structure of an induction
cooker according to the present embodiment. The induction cooker
according to the present embodiment includes a top plate 2 for placing a
pan 1 thereon, a heating coil 3 which heats the pan 1, an inverter 4
which supplies a high-frequency current to the heating coil 3 to cause
the pan 1 to generate heat through electromagnetic induction, and a
heating control unit (a control unit) 5 which controls the inverter 4.

[0045]The top plate 2 is made of a glass-ceramic or the like which
efficiently transmits infrared rays having a wavelength range equal to or
shorter than 2.5 μm. The induction cooker includes an infrared-ray
detection unit 6 which detects infrared rays radiated from the bottom
surface of the pan 1. The infrared-ray detection unit 6 is an infrared
ray sensor having a photo diode or the like which can detect wavelengths
equal to or shorter than 2.5 μm, for example. The infrared-ray
detection unit 6 includes an infrared-ray incidence section 6a for
infrared rays which is radiated from the bottom surface of the pan 1,
passes through the top plate 2, and enters the infrared-ray incidence
section 6a. The infrared-ray incidence section 6a is provided below the
top plate 2. A through hole is provided inside the infrared-ray detection
unit 6, and the upper opening of the through hole corresponds to the
infrared-ray incidence section 6a. The infrared-ray detection unit 6
includes an infrared-ray receiving element in the lower opening of the
through hole provided therein. The infrared-ray detection unit 6 directs
the infrared rays entering the infrared-ray incidence section 6a to the
infrared-ray receiving element to narrow the field of view of the
infrared-ray receiving element. As described above, the infrared-ray
detection unit 6 has a structure which gathers infrared rays radiated
from the narrow range in the bottom surface of the pan 1, while
interrupting infrared rays or disturbing light from the portion other
than the pan 1. The output from the infrared-ray detection unit 6 is
calculated by an infrared-ray temperature calculation unit 7 and
converted into the temperature of the bottom surface of the pan.

[0046]Below the top plate 2, there is provided a light emitting unit 8 for
indicating the position of the infrared-ray incidence section 6a. The
light emitting unit 8 includes an light emitter 8a such as an LED, and a
light guiding member 8b which receives light from the light emitter 8a at
a lower surface thereof and radiates the light from a light emission
surface at an upper end toward the back surface of the top plate 2. The
light emission from the light emitting unit 8 informs a user of the
position of the infrared-ray incidence section 6a. A portion of the light
radiated from the light emitter 8a with, the amount of which is not
large, also reaches lateral portions, and the infrared-ray detection unit
6 is structured to be capable of detecting such light. The light emitting
unit 8 includes a luminance changing section (not shown) which changes
the luminance for performing turn-off of light, light emission with a low
luminance and light emission with a high luminance. In the present
embodiment, while the power supply of the induction cooker is on, the
light emitting unit 8 emits light with a low luminance for indicating the
position of the infrared-ray incidence section 6a. Note that the
low-luminance light emission may be divided into a plurality of stages.
In this case, when it can be determined that no cooking is being
performed, it is possible to perform light emission in a lower stage, out
of the plurality of stages of low-luminance light emission. This can
alleviate the reduction of the life of the light emitter 8a.

[0047]The induction cooker according to the present embodiment further
includes a failure detection unit 9 which detects failures in the
infrared-ray detection unit 6, based on the amount of the change of the
output from the infrared-ray temperature calculation unit 7 which is
based on the output from the light emitting unit 8. In the present
embodiment, the failure detection unit 9 detects failures, by making a
comparison between the temperatures detected by the infrared-ray
temperature calculation unit 7 at a state where the light emitting unit 8
is turned off and at a state where the light emitting unit 8 emits light
with a high luminance.

[0048]The induction cooker according to the present embodiment further
includes a notification section 14 which gives notice that there is a
failure in the infrared-ray detection unit 6, if the failure detection
unit 9 determines that there is a failure in the infrared-ray detection
unit 9. In the present embodiment, the notification section 14 is
constituted by a display element such as an LCD or TED and is provided in
the top plate 14. The notification section 14 may also be formed as a
voice reproduction device.

[0049]Further, an operation section 13 is provided at a portion of the top
plate 2 which is closer to the user. The operation section 13 is
constituted by a plurality of key switches.

[0050]The induction cooker according to the present embodiment includes a
thermosensor 10 such as a thermistor for detecting the temperature of the
top plate 2, a heat-sensitive temperature calculation unit 11 which
calculates the temperature based on the output of the thermosensor 10,
and a temperature control unit 12 which performs temperature control
suitable for cooking such as sauteing of foods, flying of fritter,
boiling of water, cooking of rice and the like, based on the temperature
calculated by the infrared-ray temperature calculation unit 7 and the
temperature calculated by the heat-sensitive temperature calculation unit
11 and further operates to stop heating upon detecting an abnormally-high
temperature. The temperature control unit 12 has a protecting function
for stopping heating or reducing the electric power, if the output of the
heat-sensitive temperature detection unit 12 becomes equal to or higher
than a predetermined temperature (for example, 180° C.), similarly
to a protecting function based on the infrared-ray temperature.

[0051]FIG. 2 is an external view of the top plate 2. The operation section
13 includes a MENU switch 13a, a DOWN switch 13b, an UP switch 13c, and
an ON/OFF switch. The notification section 14 includes a menu display
portion 14a, a heating-power display portion 14b, and a time/temperature
display portion 14c. Further, the notification section 4 includes a
failure display portion 14d which notifies the user that a failure has
occurred in the infrared-ray detection unit 6, using an LCD display
device.

2 Operations of the Induction Cooker

[0052]2.1 Heating Operation

[0053]In the induction cooker, when the power supply (not shown) is turned
on, any of menus for sauteed-food, fritter, boil-water and cooking-rice
is selected through the MENU switch 13a, and then the ON/OFF switch 13d
is pushed to start cooking, the inverter 4 supplies electric power to the
heating coil 3 under the control of the heating control unit 5. When the
heating coil 3 is supplied with the electric power, the heating coil 3
generates an induction magnetic field, thereby heating the pan 1 on the
top plate 2. The temperature of the pan 1 is raised by the induction
heating.

[0054]If the temperature of the pan 1 is raised, the pan 1 radiates
infrared rays along with the temperature thereof. Infrared rays radiated
from the pan 1 pass through the top plate 2 and enter the infrared-ray
detection unit 6. By using the infrared-ray detection unit 6, it is
possible to detect the temperature of the bottom surface of the pan 1
with excellent accuracy. This enables the heating control unit 5 to stop
the heating or reduce the heating power, before an occurrence of ignition
even with only a small amount of oil.

[0055]2.2 Detection of Failures

[0056]The induction cooker according to the present embodiment performs
detection of failures in the infrared-ray detection unit 6 before the
start of heating. Operations of the failure detection unit 9 will be
described, with reference to timing charts of FIG. 3A to FIG. 3E. FIG. 3A
illustrates processes, FIG. 3B illustrates control of heating, FIG. 3C
illustrates light emission with a low luminance, FIG. 3D illustrates
light emission with a high luminance, and FIG. 3E illustrates the output
of the infrared ray sensor. A process 1 is a heating-stopping process
before start of heating, and a process 4 is a heating process. In the
present embodiment, the detection of failure is performed twice, between
the process 1 for stopping heating and the process 4 for heating
(processes 2a, 3a, 2b and 3b). The processes 2a, 3a, 2b and 3b are each
performed for 0.1 seconds, in the present embodiment.

[0057]In the process 2a, the light emitting unit 8 turns off the light
emission. The failure detection unit 9 stores the output of the
infrared-ray temperature calculation unit 7 at time t21 after the elapse
of 0.1 seconds since the turn off of the light emission. In the process
3a, the light emitting unit 8 emits light with a high luminance. The
failure detection unit 9 makes a comparison between the output of the
infrared-ray temperature calculation unit 7 at time t22 after the elapse
of 0.1 seconds since the start of the high-luminance light emission and
the output of the infrared-ray temperature calculation unit 7 which has
been stored at time t21 and determines whether or not the difference
therebetween is equal to or more than a predetermined value. If the
difference is equal to or more than the predetermined value, the failure
detection unit 9 determines that there is a failure in the infrared-ray
detection unit 6.

[0058]At time t22, the light emitting unit 8 turns off the light emission.
The failure detection unit 9 stores the output of the infrared-ray
temperature calculation unit 7 at time t23 after the elapse of 0.1
seconds since the turn off of the light emission. In the process 3b, the
light emitting unit 8 emits light with a high luminance. The failure
detection unit 9 determines whether or not the difference between the
value of the output of the infrared-ray temperature calculation unit 7 at
time t24 after the elapse of 0.1 seconds since the start of the
high-luminance light emission and the value of the output of the
infrared-ray temperature calculation unit 7 which has been stored at time
t23 is equal to or more than a predetermined value. If the difference is
equal to or more than the predetermined value, the failure detection unit
9 determines that there is a failure in the infrared-ray detection unit
6.

[0059]FIGS. 3A-3E illustrate a case where it is determined, based on the
failure detections at time t22 and time t24, that there is no failure in
the infrared-ray detection unit 6. Accordingly, heating is started after
time t24. If the failure detection unit 9 determines, both at time t22
and time t24, that there is a failure in the infrared-ray detection unit
6, the heating control unit 5 does not start heating and causes the
notification section 14 to notify the user that there is a failure in the
infrared-ray detection unit 6.

[0060]As described above, in the present embodiment, detection of failures
in the infrared-ray detection unit 6 is performed, based on the amount of
the change of the output of the infrared-ray temperature calculation unit
7 which is based on the turn-off of the light emitting unit 8 and the
high-luminance light emission from the light emitting unit 8. This
enables detection of failures in the infrared-ray detection unit with
excellent accuracy.

[0061]Further, immediately before the start of heating, detection of
failures in the infrared-ray detection unit 6 is performed, and the light
emitting unit 8 performs light emission with a higher luminance than in a
normal state, which can urge the user to check whether or not the
infrared-ray incidence section 6a is covered. Further, for example, when
the infrared-ray incidence section 6a is placed between the light
emitting unit 8 and the center of the heating coil 3 on the straight line
which connects the light emitting unit 8 and the center of the heating
coil 3 to each other when viewed from above, there is a high possibility
that the infrared-ray incidence section 6a is covered with the bottom of
the pan 1 if the light emitting unit is covered with the bottom of the
pan 1. That is, when the pan 1 is placed at an appropriate position, the
high-luminance light emission from the light emitting unit 8 is not
visible, but when the pan 1 is not placed at an appropriate position, the
high-luminance light emission from the light emitting unit 8 is visible.
This can prevent the user from carelessly starting heating of the pan 1
placed at an improper position, which enables stable control of the
temperature of the pan 1 through the infrared-ray detection unit 6. Note
that, when the infrared-ray incidence section 6a is placed between the
light emitting unit 8 and the center of the heating coil 3 on the
straight line which connects the light emitting unit 8 and the center of
the heating coil 3 to each other when viewed from above, if the straight
line connecting the light emitting unit 8 and the center of the heating
coil 3 to each other is made vertical to the front surface of the device
and, also, the position of the light emitting unit 8 is placed at a
position closer to the front surface of the device than the center of the
heating coil, the light emitting unit 8 is less prone to be hidden by the
pan 1 when the light emitting unit 8 is covered with the bottom of the
pan 1. This further facilitates the operation for covering the light
emitting unit 8 with the bottom surface of the pan 1.

[0062]Further, by making the luminance of the light emitting unit 8 higher
than that of normal light emission, it is possible to increase the
accuracy of the failure detection. Further, even if the luminance is
increased, only a short time is required for detecting failures, which
prevents the life of the light emitting unit 8 from being adversely
affected thereby.

[0063]Further, it is also possible to prevent heating from being started,
when there is a failure in the infrared-ray detection unit 6. This can
prevent the ignition of oil due to the start of heating during cooking,
for example. Further, the notification section 14 notifies the user that
there is a failure in the infrared-ray detection unit 6. This can improve
the safety and can also improve the convenience. Also, it is possible to
cause the light emitting unit 8 to perform display in a flashing manner,
which enables the user to easily recognize the position of the
infrared-ray incidence section 6a, thereby further improving the
usability.

3. Examples of Modifications

[0064]Although, in the present embodiment, failure detection is performed
twice and, only if it is determined twice continuously that there is a
failure, it is decided that there is a failure, and the start of heating
is prevented (the stop of heating is maintained), the number of failure
detections is not limited to that in the present embodiment. For example,
if it is determined, continuous two or more times out of a predetermined
number of detections (for example, five times), that the infrared-ray
detection unit is normal, it may be determined that there is no failure
therein, and otherwise, it may be determined that there is a failure
therein. This enables detection of failures with excellent accuracy.

[0065]It is also possible to make a comparison among a plurality of
continuous values from the infrared-ray temperature calculation unit 7 at
the same light emission state of the light emitting unit 8 (for example,
a light-turned-off state or a high-luminance lighting state) (a
comparison between the values at times t21 and t23 or a comparison
between the values at times t22 and t24), and the determination of
failure detection may be performed only if the result of the comparison
falls within a predetermined range. This can prevent erroneous detections
due to interruption of sunlight or illumination light by movement of
humans or objects.

[0066]Further, it is possible to provide a shield section which interrupts
the infrared rays entering the infrared-ray detection unit 6 from the
upper surface of the top plate 2 while the failure detection unit 9
performs the failure detection. This enables failure detection only based
on the amount of radiation of infrared rays which is based on the amount
of light emission from the light emitting unit 8, thereby improving the
accuracy of the failure detection. The shield section is only required to
have a structure which prevents infrared rays from the top plate 2 from
entering the infrared-ray detection unit 6. For example, the shield
section may be a movable shield plate provided between the lower surface
of the top plate 2 and the infrared-ray incidence section 6a. Moreover,
it is possible to realize a shield section by making the orientation of
the infrared-ray detection unit 6 variable.

[0067]Note that, while, in the present embodiment, there has been
described an induction cooker having a heating coil 3, the failure
detection can be applied to other cooking devices, provided that the
cooking devices have an infrared-ray detection unit 6 and an infrared-ray
temperature calculation unit 7. For example, the failure detection can be
applied to a high-frequency heating cooking device, a halogen cooking
device and the like.

INDUSTRIAL APPLICABILITY

[0068]The induction cooker according to the present invention is capable
of detecting failures in an infrared-ray detection unit with excellent
accuracy and, therefore, is usable as a cooking device to be frequently
used in ordinary households or restaurants.